linux-kernel - Re: [PATCH v7 05/12] arm64/boot: Factor out a macro to check SPE version

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Message-ID: <e759f728-2a77-42a7-ba92-0d5f8afe2273@linaro.org>
Date: Mon, 1 Sep 2025 13:22:40 +0100
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Jonathan Corbet <corbet@....net>,
 Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
 Zenghui Yu <yuzenghui@...wei.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Anshuman Khandual <anshuman.khandual@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, linux-doc@...r.kernel.org,
 kvmarm@...ts.linux.dev
Subject: Re: [PATCH v7 05/12] arm64/boot: Factor out a macro to check SPE
 version



On 01/09/2025 11:05 am, Leo Yan wrote:
> On Thu, Aug 14, 2025 at 10:25:27AM +0100, James Clark wrote:
>> We check the version of SPE twice, and we'll add one more check in the
>> next commit so factor out a macro to do this. Change the #3 magic number
>> to the actual SPE version define (V1p2) to make it more readable.
>>
>> No functional changes intended.
>>
>> Tested-by: Leo Yan <leo.yan@....com>
>> Signed-off-by: James Clark <james.clark@...aro.org>
>> ---
>>   arch/arm64/include/asm/el2_setup.h | 17 +++++++++++------
>>   1 file changed, 11 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
>> index 46033027510c..3a4ca7f9acfb 100644
>> --- a/arch/arm64/include/asm/el2_setup.h
>> +++ b/arch/arm64/include/asm/el2_setup.h
>> @@ -103,8 +103,7 @@
>>   	csel	x2, xzr, x0, eq			// all PMU counters from EL1
>>   
>>   	/* Statistical profiling */
>> -	ubfx	x0, x1, #ID_AA64DFR0_EL1_PMSVer_SHIFT, #4
>> -	cbz	x0, .Lskip_spe_\@		// Skip if SPE not present
>> +	__spe_vers_imp .Lskip_spe_\@, ID_AA64DFR0_EL1_PMSVer_IMP, x0 // Skip if SPE not present
>>   
>>   	mrs_s	x0, SYS_PMBIDR_EL1              // If SPE available at EL2,
>>   	and	x0, x0, #(1 << PMBIDR_EL1_P_SHIFT)
>> @@ -255,6 +254,14 @@
>>   .Lskip_brbe_\@:
>>   .endm
>>   
>> +/* Branch to skip_label if SPE version is less than given version */
>> +.macro __spe_vers_imp skip_label, version, tmp
>> +    mrs    \tmp, id_aa64dfr0_el1
>> +    ubfx   \tmp, \tmp, #ID_AA64DFR0_EL1_PMSVer_SHIFT, #4
>> +    cmp    \tmp, \version
>> +    b.lt   \skip_label
>> +.endm
>> +
> 
> Just wondering if we need to move the macro to the beginning of the
> file, so that we can define it first and call it afterwards.
> 
> Otherwise, LGTM:
> 
> Reviewed-by: Leo Yan <leo.yan@....com>
> 

It's not required, but all the other macros are defined before use and 
it looks a bit weird to not do it, so I can move it.

>>   /* Disable any fine grained traps */
>>   .macro __init_el2_fgt
>>   	mrs	x1, id_aa64mmfr0_el1
>> @@ -263,10 +270,8 @@
>>   
>>   	mov	x0, xzr
>>   	mov	x2, xzr
>> -	mrs	x1, id_aa64dfr0_el1
>> -	ubfx	x1, x1, #ID_AA64DFR0_EL1_PMSVer_SHIFT, #4
>> -	cmp	x1, #3
>> -	b.lt	.Lskip_spe_fgt_\@
>> +	/* If SPEv1p2 is implemented, */
>> +	__spe_vers_imp .Lskip_spe_fgt_\@, #ID_AA64DFR0_EL1_PMSVer_V1P2, x1
>>   	/* Disable PMSNEVFR_EL1 read and write traps */
>>   	orr	x0, x0, #HDFGRTR_EL2_nPMSNEVFR_EL1_MASK
>>   	orr	x2, x2, #HDFGWTR_EL2_nPMSNEVFR_EL1_MASK
>>
>> -- 
>> 2.34.1
>>